**5.3.3 PSM-DDD
clear
use "C:\Users\LXJ\Desktop\企业层面实证\2001-2022全样本.dta"
//最近邻匹配 1：1
forvalue i = 2008/2018{
preserve
capture {
keep if year == `i'
set seed 123
genranorder = runiform()
sort ranorder

psmatch2 treat $C, outcome(Y) logit neighbor(1)///
ties common ate caliper(0.05)

sort _id
gen pair=_id if _treat==0
replace pair=_n1 if _treat==1
bysort pair :egen paircount=count(pair)
drop if paircount!=2

save `i'.dta, replace
}
restore
}
clear all
use 2008.dta, clear
forvalue k =2009/2018 {
capture {
append using `k'.dta
}
}
save "psmdata.dta", replace
//PSM-DDD（使用满足共同支持假设的样本）
reghdfeif _support==1,absorb( ) vce(cl)

forvalue i =2008/2018 {
erase `i'.dta
}
erase psmdata.dta
//半径匹配
clear
use "C:\Users\LXJ\Desktop\企业层面实证\2001-2022全样本.dta"
forvalue i = 2008/2018{
preserve
capture {
keep if year == `i'
set seed 123
genranorder = runiform()
sort ranorder

psmatch2 treat $C, outcome(Y) logit radius///
ties common ate caliper(0.05)
drop if _weight==.
save `i'.dta, replace
}
restore
}
clear all
use 2008.dta, clear
forvalue k =2009/2018 {
capture {
append using `k'.dta
}
}
save "psmdata.dta", replace
//PSM-DDD（使用满足共同支持假设的样本）
reghdfeif _support==1,absorb( ) vce(cl)

forvalue i =2008/2018 {
erase `i'.dta
}
erase psmdata.dta

//核匹配
clear
use "C:\Users\LXJ\Desktop\企业层面实证\2001-2022全样本.dta"
forvalue i = 2008/2018{
preserve
capture {
keep if year == `i'
set seed 123
genranorder = runiform()
sort ranorder

psmatch2 treat $C, outcome(Y) logit kernel///
ties common ate caliper(0.05)
drop if _weight==.
save `i'.dta, replace
}
restore
}
clear all
use 2008.dta, clear
forvalue k =2009/2018 {
capture {
append using `k'.dta
}
}
save "psmdata.dta", replace
//PSM-DDD（使用满足共同支持假设的样本）
reghdfeif _support==1,absorb( ) vce(cl)

forvalue i =2008/2018 {
erase `i'.dta
}
erase psmdata.dta




///图片格式转换
scheme(s1mono)



twoway (scatter pvalue1 coef1, msymbol(smcircle_hollow) mcolor(black)) (kdensity coef1 ,yaxis(2) lp(solid)) ,title("") xlabel(-0.009(0.003)0.009 ,format(%6.3f) angle(0)) ylabel(0(0.2)1, format(%7.1f) angle(0) nogrid axis(1)) ylabel(0(25)150, angle(0) nogrid axis(2)) xtitle("回归系数") ytitle("P" "值" ,orientation(horizontal) axis(1)) ytitle("核" "密" "度" ,orientation(horizontal)axis(2)) xline(0, lwidth(0.2) lp(shortdash)) xline(-0.00830, lwidth(0.3) lp(shortdash)) yline(0.1,lwidth(0.2) lp(dash)) legend(label(1 "P值") label( 2 "核密度")) plotregion(style(none)) graphregion(color(white)) scheme(s1mono)